Strengthening seasonal marine CO2 variations due to increasing atmospheric CO2

The increase of atmospheric CO2 (ref. 1) has been predicted to impact the seasonal cycle of inorganic carbon in the global ocean2,3, yet the observational evidence to verify this prediction has been missing. Here, using an observation-based product of the oceanic partial pressure of CO2 (pCO2) covering the past 34 years, we find that the winter-to-summer difference of the pCO2 has increased on average by 2.2 ± 0.4 μatm per decade from 1982 to 2015 poleward of 10° latitude. This is largely in agreement with the trend expected from thermodynamic considerations. Most of the increase stems from the seasonality of the drivers acting on an increasing oceanic pCO2 caused by the uptake of anthropogenic CO2 from the atmosphere. In the high latitudes, the concurrent ocean-acidification-induced changes in the buffer capacity of the ocean enhance this effect. This strengthening of the seasonal winter-to-summer difference pushes the global ocean towards critical thresholds earlier, inducing stress to ocean ecosystems and fisheries4. Our study provides observational evidence for this strengthening seasonal difference in the oceanic carbon cycle on a global scale, illustrating the inevitable consequences of anthropogenic CO2 emissions

Bibliografía histórica sobre la Ciencia y la Técnica en España. 1997

Repertori de bibliografia històrica sobre la ciència i la tècnica a Espanya editada en 1994. //.Repertorio de bibliografía histórica sobre la ciencia y la técnica en España editada en 1994

A mechanistic account of increasing seasonal variations in the rate of ocean uptake of anthropogenic carbon

A three-dimensional circulation model that includes a representation of anthropogenic carbon as a passive tracer is forced with climatological buoyancy and momentum fluxes. This simulation is then used to compute offline the anthropogenic delta pCO(2) (defined as the difference between the atmospheric CO2 and its seawater partial pressure) trends over three decades between the years 1970 and 2000. It is shown that the mean increasing trends in delta pCO(2) reflects an increase of the seasonal amplitude of delta pCO(2). In particular, the ocean uptake of anthropogenic CO2 is decreasing (negative trends in delta pCO(2)) in boreal (austral) summer in the Northern (Southern) Hemisphere in the subtropical gyres between 20A degrees N (S) and 40A degrees N (S). In our simulation, the increased amplitude of the seasonal trends of the delta pCO(2) is mainly explained by the seasonal sea surface temperature (SST) acting on the anthropogenic increase of the dissolved inorganic carbon (DIC). It is also shown that the seasonality of the anthropogenic DIC has very little effect on the decadal trends. Finally, an observing system for pCO(2) that is biased towards summer measurements may be underestimating uptake of anthropogenic CO2 by about 0.6 PgC yr(-1) globally over the period of the WOCE survey in the mid-1990s according to our simulations. This bias associated with summer measurements should be expected to grow larger in time and underscores the need for surface CO2 measurements that resolve the seasonal cycle throughout much of the extratropical oceans

Comparative study of potential transfer of natural and anthropogenic cadmium to plankton communities in the North-West African upwelling

International audienceA Lagrangian approach based on a physical–biogeochemical modeling was used to compare the potential transfer of cadmium (Cd) from natural and anthropogenic sources to plankton communities (Cd-uptake) in the North-West African upwelling. In this region, coastal upwelling was estimated to be the main natural source of Cd while the most significant anthropogenic source for marine ecosystem is provided by phosphate industry. In our model experiment, Cd-uptake (natural or anthropogenic) in the North-West African upwelling is the result of an interplay between the Cd dispersion (by advection processes) and the simulated biological productivity. In the Moroccan waters, advection processes limit the residence time of water masses resulting in a low natural Cd-uptake by plankton communities while anthropogenic Cd-uptake is high. As expected, the situation is reversed in the Senegalo-Mauritanian upwelling where natural Cd-uptake is higher than anthropogenic Cd-uptake. Based upon an estimate of Cd sources, our modeling study shows, unexpectedly, that the anthropogenic signal of potential Cd-bioaccumulation in the Moroccan upwelling is of the same order of magnitude as the natural signal mainly present in the Senegalo-Mauritanian upwelling region. A comparison with observed Cd levels in mollusk and fishes, which shows overall agreement with our simulations, is confirming our estimates

Revisiting the La Nina 1998 phytoplankton blooms in the equatorial Pacific

A biogeochemical model of the tropical Pacific has been used to assess the impact of interannual variability in a western Pacific iron source on the iron-limited ecosystem of the central and eastern Pacific during the 1997-1998 El Nino A reference simulation and two simulations with an iron source in the western Pacific have been performed The two "source" simulations differed only in the temporal variability of the iron source. In the variable source simulation, the iron concentration in the source region was proportional to the velocity of the New Guinea Coastal Undercurrent (NGCUC) In the constant source simulation, the same time-averaged concentration of iron was imposed with no temporal variability. The variable source was designed to mimic variations of iron flux from the northeast slope of New Guinea to the NGCUC due to modulation of sedimentary iron resuspension as previously hypothesized Through the comparison of these simulations, it appeared that: (i) an iron source in the NGCUC, regardless of its source variability, increases biomass in the eastern equatorial Pacific because of the greater eastward iron flux by the Equatorial Undercurrent and (ii) a variable NGCUC iron source does not change the temporal variability of eastern Pacific chlorophyll, and in particular the timing and intensity of the June 1998 bloom To explain eastern Pacific biological variability, local rather than remote processes are needed, such as wind-driven upwelling, the local depth of the thermocline. tropical instability waves and biological processes such as high grazing pressure. Therefore, while the western Pacific sources of dissolved iron are important in our model to sustain annually integrated equatorial Pacific production, they are unlikely to strongly constrain the timing of blooms in the central and eastern Pacific such as during the 1998 La Nina (C) 2010 Elsevier Ltd. All rights reserve

Towing with sailboat robots

International audienceMoving huge objects floating at the surface of the ocean (such as containersor icebergs) with boats requires many human operators and a lot of energy.This is mainly due to the fact that when humans operate such equipment, time iscostly. Now, when we have time (as when robots operate, for instance), it is possibleto move arbitrarily large objects, for over long distances, with a limited quantity ofenergy. This is a consequence of the fact that in the water, the friction forces areproportional to the square of the speed (i.e., when we go slowly, we have almostno friction). This paper proposes the use of a sailboat robot to tow large objects. Itshows which control law could be used is order to (i) avoid loops inside the towingcable, (ii) avoid collisions between the robot and the towed object, and (iii) movethe object toward the desired direction. The control law is validated on a simulationwhere the object to be towed has to follow a trajectory corresponding to a largecircle

SCIENTIFIC COMMITTEE TENTH REGULAR SESSION

1. The SC10 notes the construction of new climate forcing data to forecast tuna distributions and abundance over the longer time frame. 2. The SC10 includes optimisation of SEAPODYM for the four tropical tuna with this new climate forcing in the future work plan of Project 62. 3. The SC notes that an additional ecosystem model for simulating climate effects on tuna, APECOSM-E has been developed and optimised for skipjack in the Indian Ocean. The optimisation of this model for skipjack in the Pacific Ocean would provide the SC with further additional advice on the impact of climate on skipjack in the WCPO. A brief summary of APECOSM-E is provided in this report. 4. The SC10 is requested to establish a new “no cost ” project for APECOSM with the objectives of applying this model to tropical tunas in the WCPO to evaluate the combined impacts of climate and fishing. The project would report back to the SC at its annual meeting. Project implementation will proceed on the basis of third-party funding. There would be no financial implications for the SC or WCPFC

Rapid evolution of an RNA virus to escape recognition by a rice NLR immune receptor

Viral diseases are a major limitation for crop production and their control is crucial for sustainable food supply. We investigated by a combination of functional genetics and experimental evolution the resistance of rice to the rice yellow mottle virus which is among the most devastating rice pathogens in Africa and the mechanisms underlying the extremely fast adaptation of the virus to its host. We found that the RYMV3 gene that protects rice against the virus codes for a nucleotide-binding and leucine-rich repeat domain protein (NLRs) from the Mla-like clade of NLRs. RYMV3 detects the virus by forming a recognition complex with the viral coat protein (CP). The virus escapes efficiently from detection by mutations in its CP some of which interfere with the formation of the recognition complex.This study establishes that NLRs confer also in monocotyledonous plants immunity to viruses and reveals an unexpected functional diversity for NLRs of the Mla clade that were only known as fungal disease resistance proteins. In additions, it provides precise insight into the mechanisms by which viruses adapt to plant immunity and gives important knowledge for the development of sustainable resistance against viral diseases of cereals